Bebe Rexha Defends Friend Wearing Sombrero and Poncho for Halloween

Bebe Rexha thinks folks who are pissed her pal rocked a "Mexican" Halloween costume ... need to chill, because she knows something that they don't.

We got the pop singer Wednesday at LAX and asked about the photo she posted that got a bit of blowback for the outfit one of her friends wore -- a sombrero and poncho. Some people claimed racism or cultural appropriation.

Well, turns out looks can be deceiving -- Bebe told us the hombre is actually her assistant, Jesús ... and, as you might have guessed by now ... he has every right to wear that gear.

Bebe told us everyone who assumed Jesús is white, just got it wrong. That said, she does believe there are rules about who can wear this costume. As she put it, you better be Mexican or very ... well, we'll let Bebe explain.